The invention concerns a plug coupling for directing a fluid under pressure, especially for breathing-protection devices, with a box-shaped receiving part and a plug part within it, into which a plug can be inserted, whereby the receiving part has a valve housing with locking means mounted inside it to lock the plug part into the plugged-in position in the receiving part and a locking sleeve cooperating with the locking means, arranged to be movable back and forth between two axial positions and also rotatable in such a way that the locking sleeve, which is spring-prestressed in the axial direction, fixes the locking and in the other axial position releases a movement of the locking means as a release position for the plug part in the locked position in the sense of removing the plug part from the receiving part, and that the locking sleeve, also spring-prestressed in the direction of rotation and can be rotated between a first rotational position and a second rotational position on the valve housing, is locked with the valve housing in its first rotational position and in its second rotational position, it permits an axial movement of the locking sleeve in the released position, and whereby an additional security device is provided, applied with the plug part plugged into the plug coupling, against a rotation of the locking sleeve with increasing pressure of the fluid led through it.
A plug coupling with the above-mentioned characteristics is known from DE 102005025548 A1, now EP 1 729 051 B1. The plug coupling described therein consists, in its parts most essential for understanding the described invention, of a base body as the receiving part and a plug part. On the base body, a locking sleeve is arranged so as to move between two axial positions, which in the first axial position establishes locking means for locking the plug part in the receiving part and in the second axial position releases the locking device in terms of removing the plug part from the receiving part. In order to make an unintentional detachment of the plug part more difficult, the locking sleeve is also arranged in such a way that it can rotate between two rotational positions so that movement of the locking sleeve from the one axial position, in which the locking means are locked, is blocked until the locking sleeve is changed from a first rotational position to a second rotational position. A fluid chamber between the base body accepting the receiving part and the locking sleeve acts as a further security measure against a detachment of the plug coupling with the plug coupling under pressure. This fluid chamber communicates with the fluid led through the plug coupling and serves to generate a force corresponding to the prevailing pressure hold to hold the locking sleeve in the locking position. The force generated is greater than the force that a user can apply by hand if he tries to move the locking sleeve into the unlocked position.
The known plug coupling is associated, first of all, with the disadvantage that the arrangement of the fluid chamber in the receiving part and its connection to the locking sleeve causes a complicated structure of the plug coupling with corresponding individual parts, which is according expensive in production and assembly. Furthermore, it is a disadvantage that securing the locking sleeve is aimed at making it more difficult to move the locking sleeve when the plug coupling is under pressure and it is therefore based on a force closing, so that, for example, at a lower pressure in the plug coupling, no adequate security against detachment of the plug coupling can be given.
The invention is therefore based on the task of improving the security of the plug coupling with the characteristics mentioned in the introduction against unlocking when the plug coupling is under pressure and at the same time simplifying the plug coupling in its structure.